Day: August 3, 2012

Motion sensing can be quite effective when taking photographs of wildlife. But how can one be sure that the motion was at the center of the frame? A PIR sensor picks up motion in its entire viewing range. It’s not really something that can be aimed. But if you use two PIR sensors you can monitor a focused area for motion.

The trick is to use a logic circuit. By building an AND gate you can trigger based on motion in the area which is overlapped by both of the sensors. In this case the AND gate is built from a voltage divider. The outputs of the PIR sensors are connected above and below the divider’s connection to the photo trigger. Both have a protection diode, and the divider is tuned so that both PIR outputs must come one in order to raise the trigger input above the voltage threshold. So much for never crossing the streams.

With the Olympics on there are a lot of really great camera shots shown during the events. One of the best is the overhead view, which is provided by a camera suspended between cables. It’s not new for the Olympics, SkyCam has been around for over twenty years. What is new is [Dan Royer’s] attempts to build his own aerial camera setup.

He’s not starting from zero with this project. [Dan] has done some really great work with the Drawbot. It’s a two-motor, two-axis plotter which uses CNC to draw on a white board. For this project he combined two Drawbots in order to add a third axis. The image above shows the camera mount suspended between the four strings. He’s been working hard on getting the software ready for this kind of addressing. Along the way he broke the strings a few times because he was too far from the kill switch to stop it in time. But what he’s got is a nice start and we hope to see a more illustrative follow-up soon.

One of the things that SkyCam has going for it is a stabilization system. We wonder if a spinning gyroscope would work as well as it did for that balancing bike.

[Steve Wozniak’s] damn the man, devil may care attitude continues to show with this recent interview. Here he shows off the pad of $2 bills he had made up. He’ll sell one sheet of them to you for $5. Do you think that’s a scam? He say’s “you’d be an idiot not to buy it for five bucks” and after we dug a little deeper, he’s right.

Now, you really need to watch the video after the break before you read the rest of this feature. Trust us, it’s extremely entertaining. [Woz] mentions that he hired a local printer to make the pads for him, but he got the paper from a high-quality print shop. They meet the specs of the federal government and by law they’re legal tender. Each pad has a page of four bills which can be torn off of the gummed top, and there are perforations between each bill for easy separation.

Nothing illegal is going on here. We followed one of the YouTube commentor’s links to this article [Woz] wrote about his $2 bill exploits. The high-quality printer he buys the paper from is the Bureau of Printing and Engraving. He buys the bills in sheets and pays a premium for that option. Each $2 bill costs him $3. But the fun he’s had over the years is probably worth it.

Confronted with a monitor that would display neither HDMI signal, nor composite video, [Joonas Pihlajamaa] took on a rather unorthodox task of getting his oscilloscope to work as a composite video adapter. He’s using a PicoScope 2204 but any hardware that connects to a computer and has a C API should work. The trick is in how his code uses the API to interpret the signal.

The first thing to do is make sure the voltage levels used in the composite signal are within the tolerances of your scope. [Joonas] used his multimeter to measure the center pole of the RCA connector and found that the Raspberry Pi board puts out from 200 mV to 2V, well within the PicoScope’s specs. Next he started to analyze the signal. The horizontal sync is easy to find, and he ignored the color information — opting for a monochrome output to ease the coding process. The next big piece of the puzzle is to ascertain the vertical sync so that he knows where each frame starts. He got it working and made one last improvement to handle interlacing.

The proof of concept video after the break shows off the he did. It’s a bit fuzzy but that’s how composite video looks normally.

[Tuomas Nylund] wanted a way to visualize the electromagnetic fields (EMF) around him. He figured the oscilloscope was the tool best suited for the task, but he needed a way to pick up the fields and feed them into one of the scope’s probes. He ended up building this EFM probe dongle to accomplish the task.

He admits that this isn’t much more than just an inductor connected to the probe and should not be used for serious measurements. But we think he’s selling himself short. It may not be what he considers precision, but the amplification circuit and filtering components he rolled into the device appear to provide very reliable input signals. We also appreciate the use of a BNC connector for easy interface. Check out the demo video after the break to see the EMF coming off of a soldering station controller, from a scanning LCD screen, and that of a switch-mode power supply.

Oh cool we’re famous

Last weekend, the Tech Team Radio Show over in Stoke-on-Trent interviewed our boss man [Caleb]. It’s a really wonderful interview, and I’m not saying that because [Caleb] signs my check. The entire show is up on Mixcloud and you can listen to the interview beginning at about 20 minutes. By the way, the guy who interviewed [Caleb] is now writing for us. Please welcome [Richard] to our motley crew.

Group buys are an awesome idea

We’ve seen Tindie, an Etsy for your electronics projects, a few times before. [emile] put up a blog post showing the impressive stats for the first month: $646 went to makers and nearly 29,000 unique pageviews. [emile] is working on a new project called Starter. This feature allows makers to gauge interest in their project and organize group buys for rare and esoteric components. We can’t wait to see this feature go live, and of course we’ll plug it when it does.

First Tindie, now fixie

[Adam] needed a way to store his bike, so he made a swinging wall mount for his fixie. The mount is bolted to a door frame and since it swings it’s never in the way.

The latest advances in blanket technology

During the opening ceremony for the Olympics, [schobi] saw some really cool light-up blankets. From this picture it really looks like these blankets are emitting light, but we have no idea how this was done. Does anyone have an idea on how this effect was produced?

Emf Electromagnetic Field Camp is a three-day camping festival for people with an inquisitive mind or an interest in making things: hackers, geeks, scientists, engineers, artists, and crafters.

There will be people talking about everything from genetic modification to electronics, blacksmithing to high-energy physics, reverse engineering to lock picking, crocheting to carpentry, and quadcopters to beer brewing. If you want to talk, there’ll be space for you to do so, and plenty of people who will want to listen.

EMF is a volunteer effort by a non-profit group, inspired by European and US hacker camps like CCC, HAR, and toorcamp. This year on Friday 31st August – Sunday 2nd September 2012 Will hold the first Uk meeting of its kind.

Events and activities will run throughout the day and into the evening, everything else (chats, debates, impromptu circus performances, orbital laser launches) will run as long as your collective energy lasts.